1. Technical Field
The present disclosure generally relates to siliconized surgical needles. More particularly, the present disclosure is directed to siliconized surgical needles having reduced tissue penetration force and methods for making such needles employing a plasma polymerization process for the application of a siliconization material.
2. Background of Related Art
The use of plasma polymerization processes to form membranes or coatings on the surfaces of substrates is known in the art. For example, U.S. Pat. No. 5,463,010 discloses substrates coated with membranes formed by the plasma polymerization of hydrocyclosiloxane monomers that possess enhanced hydrophobicity, thromboresistance, gas permeability and biocompatibility. U.S. Pat. No. 5,650,234 discloses carbonate compounds that may be bound to amine groups on a polymeric surface formed by the plasma polymerization of hydrocyclosiloxane monomers. These carbonate compounds may then be bound to bioactive compounds.
Other examples of plasma coating processes include U.S. Pat. Nos. 5,182,317 and 5,338,770 which disclose methods for producing thrombo-resistant coatings on biomedical devices and implants wherein the surface to be coated is subjected to plasma polymerization in order to create a siloxane surface onto which a plurality of amine functional groups have been bonded, reacting the amine functional groups with polyethylene oxide chains, and then reacting bioactive molecules with the polyethylene oxide chains.
The siliconization of metallic cutting edges of articles such as, for example, razor blades, hypodermic needles, scissors, scalpels, and curettes, is also known. For example, Dow Corning Corporation""s Dow Corning(copyright) MDX4-4159 Fluid has been used to siliconize cutting edges with an ambient temperature and humidity-curable mixture of an aminoalkyl siloxane and a cyclosiloxane dissolved in a mixture of Stoddard solvent and isopropyl alcohol.
Other examples include U.S. Pat. Nos. 5,258,013 and 5,458,616 which disclose coating surgical needles with a siliconization material containing an aminoalkyl siloxane and a cyclosiloxane employing ultrasonic radiation. The siliconization material can be applied in a solvent carrier, e.g., hexane or heptane.
Yet another example is U.S. Pat. No. 5,985,355, which discloses coating surgical needles by (1) coating the needle with a coating solution comprising a highly condensable polydimethylsiloxane in a solvent to form a leveling coat; (2) evaporating the solvent from the first coating; (3) curing the leveling coating to polymerize the polydimethylsiloxane; (4) applying a second coating solution over the leveling coat comprising a polydimethylsiloxane having amino and alkoxy functional groups and a solvent; and (5) evaporating the solvent from the second coating.
The previously known processes for siliconizing needles produce surgical needles in which the force of penetration is clearly reduced compared with untreated needles. However, in these needles, the force of penetration increases considerably when a tissue is pierced several times in succession with the same needle, as happens frequently in practice during operations.
It would be advantageous to provide siliconized surgical needles which continue to exhibit significantly reduced penetration force upon successive passes through tissue during a suturing operation.
It has been discovered that subjecting a surgical needle to a plasma polymerization process for the application of a silicone coating can provide a siliconized surgical needle in which the needle exhibits an average tissue penetration force below that of a standard siliconized surgical needle.
In a preferred embodiment, the surgical needle is first subjected to a plasma etching process with an ammonia and oxygen plasma to activate the surface of the needle. The needle is then subjected to a plasma polymerization process whereby aliphatic hydrocyclosiloxane monomers are polymerized on the surface of the needle to form a siloxane coating on the needles. In one embodiment, amine groups are introduced onto the polymer coating by co-polymerizing an organo-based monomer with the aliphatic hydrocyclosiloxane monomer or by carrying out a second plasma polymerization process for the introduction of the organo-based monomer. The amine groups on the polymer coating may then be reacted with carbonate polyoxyalkylenes to give polyoxyalkylene modified polymer coatings that exhibit enhanced lubricity.
After the formation of the polymer coating, the needles may then be coated with a lubricant composition. In one embodiment, the lubricant composition includes an aminoalkyl siloxane and at least one other siloxane such as a cyclosiloxane which is copolymerizable therewith. In another embodiment, the lubricant composition is a mixture that includes at least one polydialkylsiloxane having a molecular weight sufficient to provide a viscosity of the mixture of at least about 10,000 cp and at least one other siliconization material. In yet another embodiment, the lubricant composition includes a polydialkylsiloxane and at least one siliconization material which does not covalently bond with the polydialkylsiloxane. In a preferred embodiment, the lubricant composition is applied to a needle possessing a polyoxyalkylene modified polymer coating.
The expression xe2x80x9cstandard siliconized surgical needlexe2x80x9d or xe2x80x9cstandard needlexe2x80x9d as used herein refers to a commercially available siliconized surgical needle, e.g., the siliconized surgical needles attached to sutures marketed by Ethicon, Inc. (Somerville, N.J.).
While the amount of force required to achieve penetration of tissue during suturing may initially be about the same for the siliconized surgical needle of this disclosure and a presently available siliconized surgical needle, and while both needles will tend to experience an increase in penetration force with each successive passage through tissue, at the conclusion of any given number of such passages the siliconized needle of this disclosure will exhibit significantly less penetration force than the presently available needle. Thus, the siliconized needle of this disclosure will advantageously retain its initial tissue penetration characteristics to a greater extent than a presently available siliconized needle in a manner which is particularly advantageous, as it reduces the effort required in the suturing operation.